Automobile traveling along a straight road increases its speed from 61 ft/s to 79 ft/s in 180 ft. If the acceleration is constant, how much time elapses while the auto moves the 180 ft? The neck of the picture tube. This region is 1.2 cm in length, and the electrons enter with a speed of 1 × 105 m/s and leave with a speed of 1.5 × 108 m/s. What is their acceleration over this 1.2 cm.